and they worked on a system to bring the water in to san francisco. it is an impressive system looked at today. this is just a portion of the eight-mile spanning. it relies on gravity, going through a ten-mile tunnel through a drop into the pipe and into the first of two power plants. the big drop turns the turbine and the water going back to make a big drop and generates more at the power plant and then on the to big city. never does the water have to be pumped. it goes through tunnels cut into granite. ken cooper showed me a ton tunnel like the ones that carry the water. >> this country is solid rock. >> when you look at the valley you understand why people think that filling it up with water must have lost something pretty special here. >> i can understand that. at the same time, a lot of people gained something special. a loss to the beauty, but there was a beauty gained, too. it could be another yosemite valley with parking lots and burger stands. >> they say it could be different, a place as beautiful as yosemite without the cars and the burger